This invention relates to apparatus and method for removing contaminants from gas and, particularly, for removing paint overspray from the ventilating air moved through a paint spray booth.
While many air washing or scrubbing systems have been devised, only a small number of them have proven to be satisfactory to meet the demands of the automotive industry and environmental protection agencies. While some prior art washers are very efficient for certain types of paint, they have failed in meeting the necessary standards with the newly developed paints having extremely small particle sizes.
Air washers and scrubbers customarily embody one or more and frequently several washing actions, which actions may be categorized as follows and examples of which are shown in the patents listed under each category. As will be noted, several of the patented washers or scrubbers embody several of the listed actions, some as many as five.
______________________________________ 1. Spray or Cross Spray In A Tube Dye 420,378 1890 Richards 888,119 1908 Thomas 1,246,355 1917 Frey 1,999,589 1935 Saunders 2,086,514 1937 Brandes 2,090,994 1937 Fisher 2,337,983 1943 Doyle 2,621,754 1952 Tailor 3,050,919 1962 Gallagher 3,119,675 1964 Panzica 3,328,009 1967 Gallagher 3,782,080 1974 Dobias 4,239,512 1980 France 1,192,088 1959 Germany 1,157,977 1963 Canada 687,417 1964 2. Liquid Curtain, Spray or Jets Carrier 1,138,081 1915 Bingman 1,966,280 1934 Bowman 2,070,578 1937 Ludwig 2,132,826 1938 Peters 2,227,272 1940 Fisher 2,354,674 1944 Harker 2,385,077 1945 Clark 2,395,960 1946 Fenn 2,546,259 1951 Bingman 2,694,466 1954 Watson 2,719,705 1955 Paasche 2,788,954 1957 Paasche 3,123,455 1964 Hausberg 3,140,163 1964 Saubesty 3,516,230 1970 Bornert 4,045,524 1977 Walker 4,220,078(b) 1980 Germany 1,157,977 1963 Great Brit. 866,770 3. Impringement (a) or Wet Impingement (b) Dolline 1,664,670(b) 1928 Frey 1,999,589(b) 1935 Saunders 2,086,514(b) 1937 Ludwig 2,132,826(b) 1938 Fisher 2,337,983(b) 1943 Harker 2,385,077(b) 1945 Fenn 2,546,259(b) 1951 Doyle 2,621,754(b) 1952 Watson 2,719,705(b) 1955 Najarian 3,075,751(b) 1963 Gallagher 3,119,675(a) 1964 Larsson 3,138,087(a) 1964 Krantz 3,142,548(b) 1964 Dock 3,168,029(b) 1965 Wilhelmsson 3,168,030(b) 1965 Wilhelmsson 3,168,031(a) 1965 Krantz 3,170,007(b) 1965 Krantz 3,170,384(b) 1965 Wilhelmsson 3,279,156(b) 1966 Halls 3,421,293(b) 1969 Saubesty 3,516,230 1970 Bloomer 3,934,495(b) 1976 Bornert 4,045,524 1977 Walker 4,220,078(b) 1980 Donahue 4,222,319(b) 1980 Germany 823,422(b) 1951 France 1,192,088(a)(b) 1959 Germany 1,157,977(b) 1963 4. Multiple Openings Bingman 1,966,280 1934 Frey 1,999,589 1935 Brandes 2,090,994 1937 Ludwig 2,132,826 1938 Fisher 2,337,983 1943 Doyle 2,621,754 1952 Najarian 3,075,751 1963 Gallagher 3,119,675 1964 Wilhelmsson 3,279,156 1966 Dock 3,347,024 1967 Halls 3,421,293 1969 Gallagher 3,782,080 1974 Bloomer 3,934,495 1976 Bornert 4,045,524 1977 Walker 4,220,078 1980 Donahue 4,222,319 1980 France 1,192,088 1959 Canada 687,417 1964 5. Gyratory or Whirling Action Frey 1,999,589 1935 McCornack 2,047,424 1936 Peters 2,227,272 1940 Fisher 2,354,674 1944 Fenn 2,546,259 1951 Campbell 2,732,909 1956 Tailor 3,050,919 1962 Halls 3,421,293 1969 Germany 823,422 1951 Germany 1,009,635 1957 6. Atomization Frey 1,999,589 1935 McCornack 2,047,424 1936 Larsson 3,138,087 1964 Krantz 3,138,647 1964 Hausberg 3,140,163 1964 Krantz 3,142,548 1964 Wilhelmsson 3,168,031 1965 Krantz 3,170,007 1965 Krantz 3,170,384 1965 Erni 3,182,977 1965 Wilhelmsson 3,279,156 1966 Gerhard 3,795,093 1974 7. Water-washed Wall Ludwig 2,132,826 1938 Peters 2,227,272 1940 Fisher 2,337,983 1943 Clark 2,395,960 1946 Bingman 2,694,466 1954 Paasche 2,788,954 1957 Larsson 3,138,087 1964 Wilhelmsson 3,279,156 1966 Saubesty 3,516,230 1970 Gerhard 3,795,093 1974 Great Brit. 866,770 8. Venturi Throttle Bingman 1,966,280 1934 Fisher 2,337,983 1943 Fenn 2,546,259 1951 Doyle 2,621,754 1952 Tailor 3,050,919 1962 Krantz 3,112,352 1963 Gallagher 3,119,675 1964 Larsson 3,138,087 1964 Krantz 3,138,441 1964 Krantz 3,138,647 1964 Hausberg 3,140,163 1964 Krantz 3,142,548 1964 Dock 3,168,029 1965 Wilhelmsson 3,168,030 1965 Wilhelmsson 3,168,031 1965 Krantz 3,170,007 1965 Krantz 3,170,384 1965 Erni 3,182,977 1965 Wilhelmsson 3,279,156 1966 Dock 3,347,024 1967 Wilhelmsson 3,391,630 1968 Halls 3,421,293 1969 Gallagher 3,782,080 1974 Gerhard 3,795,093 1974 Bloomer 3,934,495 1976 Bornert 4,045,524 1977 Walker 4,220,078 1980 Donahue 4,222,319 1980 Dobias 4,239,512 1980 ______________________________________
Of the above listed types of washing actions and related patent disclosures, categories 2, 3, 7 and 8 are of particular import.
In the automotive industry today, paint spray booths fall principally into two categories, namely, back-section booths and down-flow booths. One patent showing an improved washer/scrubber adapted to both types of booths in Dobias U.S. Pat. No. 4,239,512.
In back section booths, the cleaning or the washing of the air is accomplished in exhaust plenums which extend along one or both sides of the booth to the exterior of the paint-spraying or work chamber. Representative illustrations of such booths are shown for example in the Harker and Gallagher patents.
In down-flow booths of current design, the cleaning, washing or scrubbing of the air takes place below the work chamber, usually along the longitudinal center line of the work chamber. The scrubbers in these booths fall into two general categories, namely, longitudinal slot washers and plural opening washers. Plural opening washers are shown for example in the patents to Halls, Bloomer, Donahue, Bornert and Walker. Longitudinal slot washers are shown for example in the patents to Dock, Krantz, Larsson, Wilhelmsson and Gerhard.
In all of the above-referenced down-flow booths, the spray painting chamber has a grille floor below which there is a water-washed subfloor over which water or other liquid medium (hereinafter referred to generically as "water") for treating the air or other gas (hereinafter referred to generically as "air") is continuously flooded. Below the subfloor is an exhaust plenum or chamber which communicates with one or more exhaust fans and stacks. In operation, air is drawn downwardly through the spray chamber, the grille floor and the opening or openings in the water washed subfloor and thus into the exhaust system. At the same time, water is continuously flooded into the opening or openings in the subfloor so that the water and air are intermixed to cause the water to remove particulates, i.e., paint overspray, from the air; the object being to remove all but an almost infinitesimal fraction of the particulates from the air so that only clean air is exhausted from the system.
The water in turn is drained to a treatment facility or "sludge farm" and then recirculated back to the subfloor of the booth.
Of particular pertinency to the present invention are the down-flow booths with slot-type washers, especially Krantz U.S. Pat. Nos. 3,112,352, Larsson 3,138,087, Wilhelmsson 3,168,030 and 3,168,031, and Gerhard 3,795,093. As shown by these patents, as well as others above mentioned, considerable effort has been expended in the art to improve and enhance an intimate admixture of the water and air to cause the water to thoroughly scrub the air free of particulate matter.
While these devices have been reasonably effective in removing paint overspray of relatively large particle size from the air exhausted from the spray chamber, they have not been entirely satisfactory with recently developed paints and spray painting systems which produce an overspray having extremely small particle size. Further disadvantages of these devices reside in their propensity for accumulation of paint deposits, inconsistency of operation over the length of the booth, and difficulty of cleaning.